Fun fact, the Marlin firmware uses a very strange way of assigning pin numbers – not Atmels way of doing it, nor the physical pin numbering on the chip, but consecutive numbers for digital pins and another set of numbers for the PORTA pins (so pin 4 means actually physical pin 5 on the Atmega644, go figure!). Fortunately there’s an ascii-schematic for the Atmega644 in pins.h – just not for the Sanguinolulu…